The private images were gathered from millions of Yahoo users with sexually explicit images among those gathered by spy agency GCHQ.

Internet giant Yahoo has denied any knowledge of the programme and has described the revelations from the Guardian as a "completely unacceptable" privacy violation.

In a statement GCHQ said all of its actions were in accordance with the law.

The operation, named Optic Nerve, was aided by the powerful US National Security Agency (NSA) and is said to have stored images transmitted between 2008 and 2010.

MARKED MAN: Former NSA analyst Edward Snowden's leaks have proved hugely embarrassing to both British and American intelligence agencies [GETTY]

“Unfortunately … it would appear that a surprising number of people use webcam conversations to show intimate parts of their body to the other person”

The report into GCHQ's Optic Nerve operation

Nearly 2m users had webcam transmissions intercepted in a six-month period in 2008.

The report originated from documents leaked by whistleblower Edward Snowden.

It suggested that sexually explicit content would be captured under the programme.

"Unfortunately … it would appear that a surprising number of people use webcam conversations to show intimate parts of their body to the other person," it read.

"Also, the fact that the Yahoo software allows more than one person to view a webcam stream without necessarily sending a reciprocal stream means that it appears sometimes to be used for broadcasting pornography."

A statement from GCHQ, which has been engulfed in controversy ever since former NSA analyst began leaking information last year, said it would not comment on matters of intelligence.

It added: "All of GCHQ's work is carried out in accordance with a strict legal and policy framework which ensures that our activities are authorised, necessary and proportionate, and that there is rigorous oversight, including from the secretary of state, the interception and intelligence services commissioners and the Parliamentary Intelligence and Security Committee.